Catechins, and particularly green tea catechins are well known in numerous uses for improving health. For example, many nutritional supplements and cosmetic formulations comprise catechins and other allegedly active ingredients, including various antioxidants, minerals, vitamins, etc. Unfortunately, most catechins, and especially epigallocatechin gallate (EGCG) are relatively unstable and tend to oxidize rapidly. Worse yet, oxidation is typically exacerbated in aqueous environment in the presence of metal ions.
Not surprisingly, numerous strategies have been reported to reduce EGCG oxidation using various strategies. For example, compositions may be formulated in the absence of oxygen. Alternatively, EGCG oxidation may be delayed by providing sacrificial compounds and/or anti-oxidants to the formulations. Antioxidants have also been combined with EGCG for other purposes, and especially to provide reduction of oxidative stress in patients that are also treated with EGCG. For example, EGCG is combined with NAC as described in U.S. Pat. App. Nos. 2003/0170319 and 2004/0063648 in formulations to treat cancer. In U.S. Pat. No. 6,299,925, EGCG is combined with NAC in an effervescent drink, while the same combination is taught in GB2385768 for animal feed. While such known combinations at least sometimes provide beneficial effects, EGCG concentrations in such composition often rapidly decline due to autoxidation or other oxidative processes. Selected cysteine conjugates with catechins were described in WO 03/024951, in which cysteine was covalently reacted with the C-ring in 4-position to form an antioxidant with increased antioxidative properties. While such conjugates may provide at least some advantages, various disadvantages nevertheless remain. Among other things, as the adduct is formed on the C-ring in 4-position, such adducts are generally not available for gallate esters of catechins (e.g., EGCG). Furthermore, such modifications will introduce a net charge into the molecule in many environments, and thereby tend to prevent passive transmembrane transport.
Therefore, while numerous compositions and methods for catechins and catechin-containing compositions are known in the art, all or almost all of them, suffer from one or more disadvantage. Thus, there is still a need for stabilized catechin compositions and methods therefor.